Showing posts with label binary star systems. Show all posts
Showing posts with label binary star systems. Show all posts

Wednesday, November 8, 2017

Weird Planets 9

How many are here for Leg 9 of the Weird Planets Tour? All of you? Okay, we’ll get started. Frankly, a lot of people stay in their hotel room for this day. After 8 straight days of viewing planets, they feel they’ve seen all the possibilities. I prefer to think that each planet has something that makes it unique. Everybody secured? Here we go.

Today we’re going to visit planets and systems discovered by the Kepler Telescope, which was the first unit designed and launched specifically to look for xenoplanets. Our first stop is the Kepler-11 system. Take a look; there are at least 5 planets, although sometimes I swear there’s 6. And they’re all packed in real close to their parent star. If this were the Earth system, all of them would be within Mercury’s orbit. And yet, this system is stable; they aren’t playing havoc with each other’s orbits. When this system was first discovered, a lot of scientists revisited the ideas about planet formation. And Kepler-11 also suggested that systems with multiple small planets might be common. It makes the Earth system a little less unique, but ups the possibility that other intelligent beings – or at least life of some kind – will eventually be found.

At about that same time, the Kepler Telescope discovered Kepler-10c, a mega-Earth planet that some called the “Godzilla of Earths”. 10c is 2.3 times the size of Earth, and 17 times heavier. I think that means if you weigh 100 pounds on Earth, on 10c you would weigh 1,700 pounds. You couldn’t stand up on 10c. You wouldn’t have enough muscles to do it. Now, 10c has a sibling, Kepler-10b, which is a lava world. We’ll catch a glance of that on our way out. The Kepler-10 system is 570 light years from Earth, and is located in the constellation Draco. Considering the naming practice, there should also be a planet called Kepler-10a. I keep asking about it, but they never add any notes about that planet, if it even exists.

In front of us, you can see a double star. Orbiting around both stars is a circumbinary planet, Kepler-16b, which some have nick-named “Tatooine”. You’ve already visited the other so-called “Tatooine”, haven’t you? In a trinary star system? Yes, that earlier 1 only orbits one of the 3 stars, so the chances of any occupants actually seeing 2 suns setting at the same time are pretty slim, but on Kepler-16b, that could be possible.

Our next planet is Kepler-22b. Yes, ma’am, I’m sure there were discoveries between 16 and 22, but they haven’t given me any information on them. They carefully pick which planets to have you view. I’m afraid we couldn’t possibly visit every planet that’s been discovered. At this point, there are thousands of them, and it would take years, even if we managed several in 1 day.

The next planet is Kepler-22b. This planet is in its system’s habitable zone, and could possibly be an actual water world, which we don’t have in Earth’s system.

A short hop away is the Kepler-36 system. Do you see the 2 planets? Just 2, and their orbits are extremely close to each other. At their closest, the distance between them is 1.2 million miles, which is only 5 times the distance between the Earth and her moon. That might make colonizing easier than Earth had in colonizing Mars.

And now we skip all the way to Kepler-186f. Does anything look familiar about this planet? Some people think there is, even if they can’t say what. Kepler-186f was the first rocky planet found in the habitable zone, so the temperature is right for liquid water. It’s also very close in size to Earth. It always makes me want to land and see what might live there. But we have to keep moving, or we’ll never get done.

Here we have the Kepler-444 system, the oldest known planetary system. Here we have no less than 5 terrestrial-sized planets, all in orbital resonance. This group shows that solar systems have formed and existed in our galaxy for nearly its entire life.

Kepler-452b is the first Earth-sized planet found in the habitable zone of a sun-like star. So it might look even more familiar than 186f did. 452b is only 60% larger than Earth, and 5% further from its star. Following our earlier logic, if you weigh 100 pounds on Earth, here you would weigh 160 pounds, which would be tiring, but do-able. And if a typical day on Earth got to 100°, here it might get to 95°. But there are a lot of things that have an influence on a planet’s temperature, so I’m not absolutely certain of that last statement. Still, at first glance, it certainly sounds inviting.

And now, just one last pause on our way back to the station. As you may know, the Kepler Telescope developed a technical problem, which scientists ‘fixed’, sort of, but its mission had to be modified to accommodate its somewhat limited capability. At that point, they stopped using ‘Kepler’ in the naming ritual and started using ‘K2’, to indicate these discoveries were made after its mission was modified.

This is the K2-3 system. We’re a bit late getting back, so we won’t stop here long. K2-3 has 3 super-Earths in orbit. If you check today’s pamphlet, the mass and radius of each is listed. The home office keeps promising to include updates on their atmosphere compositions, so if you see that information, I’d appreciate you letting me know.

And here we are. I apologize for a long day, but Leg 9 always takes longer than the home office thinks it should. Have a pleasant evening and get a good night’s sleep.

https://www.nasa.gov/feature/jpl/20-intriguing-exoplanets

www.space.com/159-strangest-alien-planets.html

Thursday, October 19, 2017

Weird Planets 8

Good morning. I am your replacement driver and tour guide. Your previous driver, um, has been... has been asked to stay home today.

Hope you had a large breakfast, because we’re going to visit several ‘HD’ systems on this leg, and it could be a long time until supper. Everybody buckled in? If not, get that way, ‘cause we’re headed out.

Okay, on the right side is HD 106906 b. It’s 11 times the size of Jupiter. Yes, it does have a parent star. It’s one of those bright bits of light ahead of us. This planet’s distance from its star is 650 times as Earth’s distance from our sun, so I can’t blame you for asking. Despite being so remote from its star, the average temperature on the surface is 1500° Celsius, which is 2,732° Fahrenheit. That’s pretty toasty warm, in my mind. Scientists say it shouldn’t exist at all, being so large and so far from its parent. Where did it get enough material that far out? But however it came to exist, it’s only 13 Million years old. Just a baby, really, since the universe is over 14 Billion years. So maybe it just hasn’t had a chance to cool off since it came into being?

Now, right over here is Osiris, more formally known as HD 209458 b, which was the first planet to be seen as it crossed in front of its star. It’s also the first planet to have its light directly detected. Its discovery showed that transit observations were possible, which opened up a whole new realm of exoplanet discovery.

The planet ahead of us is HD 189733 b. It’s about the size of Jupiter, and has been studied quite a bit ever since scientists discovered it transiting its star while they studied that star using X-ray frequencies. This is also one of the first planets to have its atmosphere ‘sniffed’ to determine its composition. I don’t remember the full list, but I do remember that the atmosphere contains methane. No, that doesn’t necessarily mean there’s cows on that planet. Methane can be produced naturally. It doesn’t have to be a biological byproduct.

Now we come to HD 114762 b, which was discovered in 1989. This is the first discovered planet to be orbiting a sun-like star. However, because its mass is - as seems so popular - 11 times that of Jupiter, and because it only takes 84 days to complete an orbit, it was initially thought to be a brown dwarf. But it’s not. As a comparison, tiny little Mercury takes 88 days to complete an orbit around our sun.

I have to ask you to please be quiet as I approach this one. If it was up to me, we wouldn’t even bother with this one. Too dangerous, if you ask me; you never quite know what to expect from HD 80606 b. It’s orbit is so eccentric-- Oh! Hang on! ... Whew! That was close. I think we’ll be safe now, at least for a few minutes. Besides its highly eccentric orbit, HD 80606 b also displays plenty of storms and atmospheric heating, and you can plainly see how fast it rotates.

Okay, that’s our tour for today. I’ll take you back to base so you can get some supper. I know I’m ready for it. No, I’m sorry, I don’t know who will be your next driver and tour guide. No, I don’t know where you’ll be taken, either. From the looks of it, you still have quite a number of planets to visit. We are all qualified drivers and tour guides, ma’am, otherwise, we wouldn’t have the job.

http://www.express.co.uk/news/science/643662/The-10-weirdest-planets-to-have-been-discovered-so-far
https://www.nasa.gov/feature/jpl/20-intriguing-exoplanets

www.space.com/159-strangest-alien-planets.html

Thursday, October 12, 2017

Weird Planets 7

We are about to start our whirl-wind tour of some of the remaining weird planets, but first, please pay attention to the following non-safety-related information:
Who designed the way stars and planets are named? I’ve more or less figured out how it works, but it really doesn’t give you any information about that star or planet. First, there’s some designation that I think indicates who/what ‘discovered’ the star. I recognize ‘Kepler’, which in its 2nd stage of life is denoted as ‘K2’. But WASP? CaRoT? No Idea. Then comes a number to designate the star. And finally, a letter to designate the planet within that star’s system. The planets are lettered as they are found, so smaller planets probably have later letters than big planets, even if they are closer to that star.

Please keep your hands and legs inside this blog at all times, as I am both driver and tour guide, and we have a lot of space to cover!

The first planet we’ll visit in this 3rd leg of our tour is PSR J1719-14 b (AKA the Sun Hugger), which is only 3,900 light-years from Earth. This is a possible member of the diamond-planet family (I told you about one of those in an earlier blog), and it races around its star in only 2.2 Earth hours, which makes it the fastest planet in the Ultra-Short-Period-Planet category. Also, it’s a pulsar planet, because its star is a pulsar.

Now, out the other window, take a peek at PSR J1719-1438-?, another pulsar planet orbiting a pulsar 4,000 light-years from Earth. Scientists think this planet was once a star, but when its companion became a pulsar, the huge gravity field stripped most of it away, leaving it with only the mass of Jupiter, and exerted pressure on what was left to make it a diamond planet.

Now around here – somewhere – we can see the PSR B1257+12 system discovered in 1992 and 1994. These pulsar planets at one time were the smallest planetary bodies known to exist outside our own solar system.

Here we’ve reached 12,400 light years from Earth to view PSR 1620-26 b (AKA Methuselah). As you might have guessed, it got its nickname by being old. Too old, some say, because it’s 13 billion years in age, almost 3 times as old as Earth! It would have formed less than 1 billion years after the Big Bang, even though it was thought there wasn’t enough material (I assume they mean heavier elements) to create a core for a planet. So, what’s it made of? I don’t know, they didn’t say. At that distance, maybe they can’t tell. So how do they know how old it is? Do you suppose they counted its wrinkles? J

Okay, you can take a little break now while I get us in another section of the universe.

http://www.popularmechanics.com/space/deep-space/g1265/space-oddities-8-of-the-strangest-exoplanets/
www.space.com/159-strangest-alien-planets.html
https://www.nasa.gov/feature/jpl/20-intriguing-exoplanets


Thursday, October 5, 2017

Weird Planets 6

Some of these planets look familiar, which is how they get their nicknames. Is it a surprise that someone has imagined planets similar to actual exoplanets?

HD 188753 is sometimes called Tatooine. It is a Jupiter-sized planet located 149 light-years away from us… in a triple star system. One list explained that this meant the planet orbited a star, which orbited another star, which orbited a third star. They could be right that HD 188753 is set up this way, but it is not the only configuration available to 3 stars and 1 planet. How many other configurations can you come up with?

Whatever the configuration of this system, the gravitational fields would be complex, so scientists were surprised to find planets could be created in such a gravity maelstrom. Dr Maciej Konacki of CalTech feels the view from this planet would be spectacular, with ‘occasional’ triple sunsets. Yes, that’s possible; it depends on the distance between the triplet stars. Some ‘companion’ stars are so far apart that each appears as only a bright point to the other. But this Tatooine would definitely be hot; it completes an orbit around its star in 3.5 Earth days, so it is snuggled up real close.

CoRoT-7b was the first exoplanet to be dubbed a ‘Super Earth’. That means it’s a rocky planet, not a gaseous one. Knowing that other rocky planets exist, scientists can look for potentially habitable planets that reside in a star’s ‘Goldilocks’ zone.

However, this particular planet does not look like a pleasant place, as it is tidally locked to its star, meaning the same side always faces the star, and the temperature on that face is around 4,000° F. If you want to visit, consider that it may be the rocky core of a vaporized gas giant where it rains rocks. Be sure you take a strong umbrella with you!

Kepler-10b is the first rocky planet discovered by the Kepler equipment. It is the smallest known exoplanet; an Earth-sized world that may have a lava ocean on its surface. I love a hot tub, but that’s too hot.

OGLE-2005-BLG-390 is the first ‘cold super Earth’ exoplanet discovered, nicknamed Hoth. The thought is that it began to accumulate a Jupiter-like core of rock and ice, but didn’t stop with just a core. It is 5.5 times the mass of Earth, has a surface temperature of -364° Fahrenheit, and orbits a red dwarf star some 28,000 light-years away.

Well, on this trip, we’ve gone from Tatooine to Hoth. Have we gotten all the ‘extremes’ done? I’m not sure. But next week, we’ll start zipping through the planets that only appeared on 1 list. Bring your seat belt!

http://www.express.co.uk/news/science/643662/The-10-weirdest-planets-to-have-been-discovered-so-far
https://www.nasa.gov/feature/jpl/20-intriguing-exoplanets

www.space.com/159-strangest-alien-planets.html

Wednesday, July 5, 2017

Fireballs Are Flying!

Try to imagine you are an astronomer, studying another star some 2,000 light years away, V Hydra. It’s an odd star; bloated, red, old, and pulsing - getting brighter, then dimmer, and sometimes getting much dimmer. It may be nearing the end of its life, to start again as a planetary nebula, and if that happens during your lifetime, you want to see it.

And then it throws fireballs.

No, it doesn’t explode. No, these aren’t corona ejections. They are fireballs.

How did it do that?

In October 2016, astronomers were left scratching their heads as Hubble revealed that’s exactly what happened. They studied the star and its surroundings, and eventually they came up with a theory.

V Hydra has a visible companion star (we’ll call it NNS - No Name Star, because they never mentioned a name for it). NNS is an orange dwarf about 46” distance from V Hydra. Yeah, I know, 46 inches doesn’t make any sense to me, either, but that’s actually 46 arcseconds in astronomy notation. They ‘measure’ the distance between these 2 stars by noting the angle change from looking at one to looking at the other. An arcsecond is 1/60th of an arcminute, which is 1/60 of a second... Look, take 2 meter sticks and lay one on top of the other. Stick 2 pieces of paper between them at one end. The angle at the opposite end is about 50 arcseconds. So V Hydra and NNS look like 2 bumps together from Earth, but being 20,000 light years away from us, there’s a good bit of distance between them. Chances are anything NNS might be doing would not cause V Hydra to throw fireballs around.

It appears that V Hydra has a second companion star, this one too dim to be seen directly from Earth, but astronomers have their magic math formulas to figure these things out. We’ll call this one DIM, because it’s so dim. Anyway, DIM orbits V Hydra every 8.5 years in a very elliptical orbit. This orbit is so elliptical that - now that V Hydra is bloated in its death throes - DIM no longer comes close to V Hydra, it actually travels through V Hydra’s outer atmosphere. Wow. Hot enough for ya?

As DIM travels through V Hydra’s outer atmosphere, it greedily grabs a bunch of V Hydra’s material and stores it in a disk about itself. Remember, planets are born from left-over materials in a disk around the new-born star, so I guess maybe DIM wants to start a family.

But, alas, DIM just isn’t very smart, and starts sending its ‘fledgling planets’ away long before they actually make planets. When DIM emerges from V Hydra’s atmosphere, its storage disk breaks apart, forming superhot blobs of plasma about twice the size of Mars that are tossed into the unknown at a speed that they could travel from the moon to Earth in about a half hour.

Poor DIM. Heart-breaking, isn’t it? Now consider that astronomers believe this has been happening every 8.5 years for about 400 years.

The mind boggles, right? But what can we do? I mean, sending DIM a sympathy card every 8.5 years is a bit much, don’t you think? Probably doesn’t want to talk about it, anyway.

How much would it cost to send a card 20,000 light years? Will a regular stamp do?


http://www.astronomy.com/news/2016/10/cannonballs-shooting-from-star

https://en.wikipedia.org/wiki/V_Hydrae

Thursday, May 18, 2017

Planets Around Failed Stars

Stars can (but don’t necessarily) have a family of planets surrounding them. Planets can (but don’t necessarily) have moons surrounding them. What about the so-called ‘failed stars’? Do they have anything as a family?

Jupiter is sometimes called a failed star. If it had just a bit more mass, fusion could start, goes the argument. Well, not really. It would take 13 Jupiters combined to have enough mass to reach the minimum needed for a brown dwarf, AKA failed star. Also, Jupiter was created within the disk of dust that surrounded our infant sun, which is how planets are made, not stars. Not even failed stars. So we can’t take any clues from Jupiter about the possibility of planets around dwarf stars.

Okay, so exactly what is a failed star? A close apparent brown-dwarf-type object to Earth is SIMP0136. It lies 21 light-years away and is 13 times the mass of Jupiter. Theoretically, it could be a brown dwarf. Brown dwarves form like other stars, but fail to get big enough. They may have some fusion of deuterium for a relatively short time inside them, but it doesn’t last. Any light they produce tends to be in the red and infrared spectrums, so despite being called brown dwarves, they would probably appear magenta or possibly red-orange. And the older the brown dwarf is, the more it cools and contracts, until it can seem to be just another planet. Scientists have recently decided SIMP0136 is just a planet, after all. A rogue planet, big enough and close enough for them to study its weather patterns.

It could have gone the other way. The size of brown dwarves range from a minimum of 13 Jupiter masses to a maximum of 80 Jupiter masses. If it managed to gather more than 80X Jupiter’s mass, it would have made it to actual stardom.

Because brown dwarves are a type of star, at least some of them do have a family of planets, such as 2M1207b and MOA-2007-BLG-192Lb. This makes sense, because brown dwarves form the same way as other stars, just in the middle of a smaller dust cloud. Once the center of the cloud collapses into a proto-brown-dwarf, the remainder of the cloud thins into a rotating disk of dust, which would normally form planets. It is thought that this disk would not extend far, since the entire cloud was small to begin with, so any resulting planets would be fairly close to the brown dwarf. It is also believed that these planets would be rocky, like Earth and Mars, rather than gas giants like Jupiter, because most of the gas would be taken by the brown dwarf. So, let's look at some known brown dwarf systems:

170 light years from Earth, planet 2M1207b orbits a brown dwarf. Its mass is somewhere between 3X and 10X that of Jupiter, and it orbits its primary at approximately the same distance as Pluto from our sun. Although there is some indication of water, it is not likely to be habitable.

Occasionally shortened to MOA-192 b, MOA-2007-BLG-192Lb is about 3,000 light-years away. This small planet is 3.3X Earth’s mass, and circles a small brown dwarf in an orbit approximately 2/3 the size of Earth’s orbit around the sun. It is believed to have lots of ice and gases, more like Neptune than Earth.

And then there’s the quadruplets: a small brown dwarf (2MASS J04414489+2301513, with a mass 20X that of Jupiter) has a companion (5X to 10X the mass of Jupiter) that could be either a planet or a sub-brown dwarf. There are also two other brown dwarves in close association. All four objects together only have 26% the mass of our sun, making it the quad system with the least mass. It is 470 light years away.

So yes, it is entirely possible - almost probable - that ‘failed stars’ will have planets. Or possibly siblings, as in the quad system.


http://www.iflscience.com/space/one-of-earths-closest-failed-stars-may-actually-be-a-rogue-planet/
http://now.space/posts/gas-giant-planets-small-failed-stars-is-there-a-difference/
https://en.wikipedia.org/wiki/Brown_dwarf
https://en.wikipedia.org/wiki/2M1207b
https://en.wikipedia.org/wiki/MOA-2007-BLG-192Lb
https://en.wikipedia.org/wiki/2MASS_J04414489%2B2301513

Sunday, March 2, 2014

A 500 Year Summer

My husband has been re-watching Game of Thrones. As I've said before, I don't like political intrigue, nor a cast of thousands, so this is not my cup of tea. But the characters mention they are ending a summer of 500 years, and the winter will soon be on them. That comment has me intrigued.
What kind of solar system would they be in that a season could last for hundreds of years?
I read a book many years ago - I don't remember the title or the author, sorry - where the planet's orbit was a lop-sided elliptical around its sun. When winter came, everything hibernated, even the people. The length of their year did not equal one of ours, but a year - one revolution around their sun - did involve seasons. So that wasn't the answer.
I then thought about the planet NASA has discovered that has 4 suns. That in itself is mind-boggling. The planet revolves around one star, which is in a mutual revolution with a second star, and that pair of stars is in a mutual revolution with another pair of stars.
I don't have enough math and physics to do any computations, so I just have to use some logic to try and get a feel for it. The first pair of stars have to be far enough away from each other that they don't tear each other apart, and also so they don't burn the planet to a crisp when it passes between them. But when that planet is between them, it would be extra warm. As the stars go around each other, that extra warmth would move around their calendar, until the 'extra warmth' was actually during their winter. It might not seem like they were having any winter.
How long would it take for this 'extra warmth' to move around the planet, from producing warm autumns through not-really winters and into warm springs? I don't know. It would depend on how long it takes for those 2 stars to revolve around each other. A thousand years might be too fast.
That might help explain a REALLY LONG summer, but it doesn't explain an equally long winter. When both stars were on the same side of the planet, they would have hot summers and cold winters. Bummer. I thought I might be on to something.

Do we have any physicists in the audience who would like to weigh in on this?

Sunday, December 23, 2012

One Planet With Four Suns


SF authors are not adverse to exploring alien planets. I remember a story that took place on a planet that had a severely elliptical orbit around its sun. I don’t remember details of the orbit, but let’s say it took this planet 100 Earth years to go around its sun once. For about 75 of those years, the planet was too cold to sustain life. Everything hibernated. As the planet finally approached the sun, things thawed out; people, plants and animals woke up and went about their business. They would have about 8 (of our years) of an ever-warming spring, an equally long hot, hot summer and then a gradually cooling autumn before they all hibernated again. Weird, huh?
A lot of planets these authors explore have multiple moons. Sometimes a colony would be on a world orbiting a binary star. I was as fascinated by reading about these unusual planets as the authors were in their exploration of them.
At that time, the existence of planets outside our own solar system was an unknown. These days, scientists seem to be finding them all over the place, and the assumption is that they’ve only seen the glint shining off the iceberg.
I was thumbing through the latest Discover magazine, which goes through the top 100 discoveries made in 2012. It states over 100 planets were discovered in 2012, and it had brief descriptions of 3 of them. The one that really caught my attention was PH1, which orbits a binary star. That was enough to make me remember the unusual planets I read about as a kid, but PH1 doesn’t stop there. PH1’s binary stars are also orbited by another binary star!
Try and imagine what days and nights would be like on PH1. I’ve tried, but my brain circuits tend to start sizzling after a while. To get you started, remember that 2 suns would be in the sky each day, although twice a year, one of those stars would be behind the other. The other two suns would be even further away, I assume, and I’m not sure how close they would need to be in order to be seen from the planet as ‘small suns’ and not just a pretty light. If they are seen as little suns, they would spend most of their time also in the daylight sky, perhaps disappearing behind the big suns, or being faded out by the light of the big suns. At regular intervals, however, the little suns would emerge from behind the big suns and move around to the night time sky for several years until they slipped back into the daytime again.
And that brings us to nomenclature and religion of any people living on PH1. Would they call it First and Second sunrise, First and Second sunset, with a special term for when the main suns appear to be merged? Would they have special terms for the ‘night suns’? Would the small suns be seen as ‘enemies’, sneaking behind the planet for nefarious means? What do you think?
I’m going to put this in a pot on the back burner and see if a story grows.

Sunday, September 23, 2012

Conjoined Fraternal Twins


Conjoined twins used to be called ‘Siamese’ twins. They were connected somewhere; the chest, the hip, the top of the head. Sometimes they can be separated, but other times they share some vital organ that can’t be separated. Fraternal twins come from 2 different eggs, so the resulting babies are not identical.
But what I really want to talk about is this cool binary star system I heard about a few weeks ago. When you want to write science fiction, you have to try to keep up with science, so I dip into that huge pool of information every chance I get.
I already knew about binary stars. Two stars orbit some spot between them. But this particular binary star system had stars that were far closer than any that had been found before. Really close!
The stars were not identical; one was larger, the other smaller. That’s pretty common with binary stars, so let’s call them fraternal twins.
But when the astrophysicists studied the ‘output’ of this particular pair of stars, expecting them to have different brightness because of the difference in size, they found that the smaller star had the same corona signature as its big brother. These two stars are actually sharing corona matter! To me, that says ‘conjoined’.
Who would have ever believed that a pair of stars could exist so close to each other than they could share ‘skin’, and yet remain separate entities? Why doesn’t their mutual gravity make them merge into one star? They have to be racing around each other at a super speed in order for that outward force to counter-balance the gravity.
Now I’m wondering, ‘Are these stars still spheroid?’ Or are they mis-shapened by the horrendous forces they must contend with every second? And if they are mis-shapened, what shape are they? Teardrops with the points aimed at each other? Or are they oblate spheroids, spheres that have been squashed?
The neat thing about science is that it doesn’t just answer questions, it raises even more questions for you to ponder. I’m going to speculate about this particular pair of conjoined fraternal twins for some time.