APOD: 4000 Exoplanets (2019 Jul 10)

[APOD Robot]

4000 Exoplanets

Explanation: Over 4000 planets are now known to exist outside our Solar System. Known as exoplanets, this milestone was passed last month, as recorded by NASA's Exoplanet Archive. The featured video highlights these exoplanets in sound and light, starting chronologically from the first confirmed detection in 1992. The entire night sky is first shown compressed with the central band of our Milky Way Galaxy making a giant U. Exoplanets detected by slight jiggles in their parents-star's colors (radial velocity) appear in pink, while those detected by slight dips in their parent star's brightness (transit) are shown in purple. Further, those exoplanets imaged directly appear in orange, while those detected by gravitationally magnifying the light of a background star (microlensing) are shown in green. The faster a planet orbits its parent star, the higher the accompanying tone played. The retired Kepler satellite has discovered about half of these first 4000 exoplanets in just one region of the sky, while the new TESS mission is on track to find even more, all over the sky, orbiting the brightest nearby stars. Finding exoplanets not only helps humanity to better understand the potential prevalence of life elsewhere in the universe, but also how our Earth and Solar System were formed.

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[E Fish]

I remember when I was in high school ('97 or '98), reading about the amazing discovery of a grand total of five exoplanets, all much larger than Jupiter. In fact, I was so amazed by it that I cut the article out of the Parade magazine and kept it for years. The concept of over 4,000 planets, many Earth-sized, is still a little shocking, even though I've read about new discoveries as they come out.

[wolfie138]

Any reason why there's such a dense cluster in such a "small" area in the upper left?

[Confused]

Over 4000 planets are now known to exist outside our Solar System.

Why has that dropped so drastically? I thought there are (believed to be) billions of stars, most with planets. Or that statement is wrong.

[Chris Peterson]

Over 4000 planets are now known to exist outside our Solar System.

Why has that dropped so drastically? I thought there are (believed to be) billions of stars, most with planets. Or that statement is wrong.

That's still true... the conclusion of a statistical analysis. The value of 4000 is for planets actually detected. Planets known to exist.

[Ann]

Any reason why there's such a dense cluster in such a "small" area in the upper left?

Isn't that the area where the Kepler space telescope was busy detecting planets for a couple of years?

Ann

[heehaw]

Hmmm...I feel that this is overkill; says nothing really. All the planets are nearby; the Galaxy background is totally irrelevant. Did remind me of a huge laugh I got many years ago, when pulsars had been discovered, and about 40 were known: someone made a physical model map of the galaxy with each pulsar a tiny light bulb, and they all pulsed away, with their correct periods of course! It was really fun to watch! (My laugh came when someone asked if the relative phases were correct!)

[wolfie138]

Any reason why there's such a dense cluster in such a "small" area in the upper left?

Isn't that the area where the Kepler space telescope was busy detecting planets for a couple of years?

Ann

yeah, but why s many? just because they spent so much time looking? that could suggest the same density everywhere, if they look long enough.

[Ann]

Hmmm...I feel that this is overkill; says nothing really. All the planets are nearby; the Galaxy background is totally irrelevant. Did remind me of a huge laugh I got many years ago, when pulsars had been discovered, and about 40 were known: someone made a physical model map of the galaxy with each pulsar a tiny light bulb, and they all pulsed away, with their correct periods of course! It was really fun to watch! (My laugh came when someone asked if the relative phases were correct!)

Click to view full size image

The Milky Way. Map: Martin and Tatjana Kesküla/Knut Lundmark/Lund University.

I think you may have seen the "pulsarium" in our observatory in Oxie, Malmö!

I can't find a video of it, and I can't find an English-language description of it, but the description of it in Swedish is here. I'll try to translate it, so here goes.

knutlundmark.se wrote:This famous map of the visual stellar sky in galactic coordinates was made at the Institute of Astronomy at Lund University in the beginning of the 1950s...

The map was finished in 1955.

The Pulsarium in the Tycho Brahe Observatory at Oxie, Malmö

At the Tycho Brahe Observatory we realized that we had a good chance of expanding the concept of the map. Through our contacts with the Observatory of Lund we were given a photographic full-size copy of the famous Milky Way map. We drilled holes in it for 50 lamps...

Our then-member Mikael Nyqvist made each lamp blink at the same frequency as the pulsar that each lamp represented.

In the mid-nineties the observatory was destroyed in a fire, and the pulsarium was destroyed as well. We rebuilt the observatory and made a copy of the famous map that was 20% larger than the original, and we drilled holes in it for 100 lamps. We also used more up-to-date electronics to make the pulsars blink. This masterpiece is admired by all visitors to our observatory...

You're welcome to visit the Tycho Brahe Observatory in Oxie, Malmö, to take a closer look at the pulsarium, heehaw!

Ann

[orin stepanek]

The bigger the planet; the easier to find! I'm thinking that a lot of the stars that have planets discovered around them, still have more planets around them them that haven't been discovered yet!

[Ann]

Any reason why there's such a dense cluster in such a "small" area in the upper left?

Isn't that the area where the Kepler space telescope was busy detecting planets for a couple of years?

Ann

yeah, but why s many? just because they spent so much time looking? that could suggest the same density everywhere, if they look long enough.

I don't know why Kepler spent so much time looking at more or less the same spot, but I'm sure there was a good reason for it.

You are quite right that astronomers expect that there will be just as many planets everywhere else, too.

Ann

[jschneider]

4000 exoplanets?

The NASA Exoplanet Archive is behind the real counts.
There are as of July 10 at least 4098 exoplanets:
http://exoplanet.eu/catalog/

In addition the NASA archive is ambiguous since they do not give their adopted mass limit for exoplanet.

Jean Schneider
Paris Observatory
http://exoplanet.eu

[workgazer]

But how many of these will be blue?
perhaps Lund could take a secound copy of the galaxy map and now put a light for each plannet found?

[De58te]

Isn't that the area where the Kepler space telescope was busy detecting planets for a couple of years?

Ann

yeah, but why s many? just because they spent so much time looking? that could suggest the same density everywhere, if they look long enough.

I don't know why Kepler spent so much time looking at more or less the same spot, but I'm sure there was a good reason for it.

You are quite right that astronomers expect that there will be just as many planets everywhere else, too.

Ann

Kepler's orientation in its trailing orbit of Earth was kept oriented towards the constellations of Cygnus, Lyra and Draco, so as to keep sunlight out of the telescope and to keep the solar arrays pointed to the Sun for maximum efficiency. However, on July 14, 2012, one of the spacecraft's four reaction wheels used for pointing the spacecraft stopped turning, and completing the mission would only be possible if all other reaction wheels remained reliable.[17] Then, on May 11, 2013, a second reaction wheel failed, disabling the collection of science data[18] and threatening the continuation of the mission.[19] On August 15, 2013, NASA announced that they had given up trying to fix the two failed reaction wheels. This meant the current mission needed to be modified, but it did not necessarily mean the end of planet hunting.-Wikipedia. This complication apparently further narrowed the range Kepler had to work with. However in 2013 a new proposal was applied, 'K2, Second Light' which allowed Kepler to gather information from a drifting star instead of Kepler having to fix on a star. Thus its field of view was actually expanded but its scientific discoveries still declined because of its limited manoeuvrability.

[Osh]

I wonder, is the size of the identifying "circle" relevant?

[Chris Peterson]

Any reason why there's such a dense cluster in such a "small" area in the upper left?

Isn't that the area where the Kepler space telescope was busy detecting planets for a couple of years?

Ann

yeah, but why s many? just because they spent so much time looking? that could suggest the same density everywhere, if they look long enough.

Almost certainly the density is the same everywhere. Most planets can't be found using this technique, though. But we can assume they are there, since orientations are entirely or largely random.

[neufer]

I wonder, is the size of the identifying "circle" relevant?

<<On June 13, 2019, the number of known exoplanets passed 4000 according to the NASA Exoplanet Archive! To celebrate, we have animated their discoveries in time and converted them into music. A circle appears at the position of each exoplanet as it is discovered with a colour that indicates which method was used to find it (see below). The size of the circle indicates the relative size of the planet's orbit and the pitch of the note indicates the relative orbital period of the planet. Planets with longer orbital periods (lower orbital frequencies) are heard as low notes and planets with shorter orbital periods (higher orbital frequencies) are heard as higher notes. The volume and intensity of the note depends on how many planets with similar orbital periods were announced at the same time. The discovery of a single planet will be quiet and soft while the discovery of many planets with similar periods is loud and intense. The quiet background hum is created by converting the colours of bright stars that appear in the Milky Way into sound. Radial Velocity (Pink), Transit (Purple), Imaging (Orange), Microlensing (Cyan), Timing Variations (pulsar, transit, eclipse, pulsation) (Red), Orbital brightness Modulation (Yellow), Astrometry (Grey).>>

[neufer]

Isn't that the area where the Kepler space telescope was busy detecting planets for a couple of years?

yeah, but why s many? just because they spent so much time looking? that could suggest the same density everywhere, if they look long enough.

Almost certainly the density is the same everywhere. Most planets can't be found using this technique, though. But we can assume they are there, since orientations are entirely or largely random.

Fortunately, the Kepler transit exoplanets tends toward small orbits resulting in small graphic circles.

[TheZuke!]

Is the Milky Way "s" shaped because of the orbit of the satellites?

[neufer]

Polar Orbiting Environmental Satellites (POES) Neufer worked on

---

Is the Milky Way "s" shaped because of the orbit of the satellites?

The Milky Way "S" shape is because the apparent great circle orbit of the Milky Way around the Earth generates a sinusoidal "S" shape (as does every other Earth satellite orbit) when mapped against the Earth/Sky.

[peterjford]

I am starting to wonder if there are any stars that do not have planets. I am sure many stars that have been looked at did not show evidence of a planet, but have and stars been confirmed to not have a planet?

[BDanielMayfield]

I am starting to wonder if there are any stars that do not have planets. I am sure many stars that have been looked at did not show evidence of a planet, but have and stars been confirmed to not have a planet?

That's an interesting idea Peter. Planet formation has been discovered to be a byproduct of star formation, so when a star forms, it is very likely that planets will be forming right along with it. Sometimes however planets can get ejected from the system they formed in, so a star could loose planet(s) and become planet-less. Also stars likely destroy many planets as they swell into giants as they age.

The fact that most individual stars are parts of multiple star systems makes this somewhat more complicated too. Very close binary stars cannot have a planet in a stable orbit of just one of the pair, but they can have planets orbiting both stars (more precisely their common barycenter). Systems of three, four, etc. stars can start out with planets, but gravitational stability rules if and where planets can remain over astronomical time scales.

Many stars in globular clusters probably don't have planets. But you asked if any stars have been confirmed to be planet-less. That answer is probably no, but on theoretical grounds it is very likely that some (low?) percentage of star systems don't have planets.

Bruce

[Ann]

Polar Orbiting Environmental Satellites (POES) Neufer worked on

---

Is the Milky Way "s" shaped because of the orbit of the satellites?

The Milky Way "S" shape is because the apparent great circle orbit of the Milky Way around the Earth generates a sinusoidal "S" shape (as does every other Earth satellite orbit) when mapped against the Earth/Sky.

Wow, Art. You've made 16061 posts. That's a "palindrome number". And impressive, too.

Ann

[neufer]

---

Wow, Art. You've made 16061 posts. That's a "palindrome number". And impressive, too.

palindrome (n.) "line that reads the same backward and forward," 1620s, from Greek palindromos "a recurrence," literally "a running back." Second element is dromos "a running" (see dromedary); first is palin "again, back."
...........................................
dromedary (n.) "thoroughbred Arabian camel," late 13c., from Old French dromedaire and directly from Late Latin dromedarius "kind of camel," from Latin dromas (genitive dromados), from Greek dromas kamelos "running camel," from dromos "a race course," from dramein "to run." An early variant in English was drumbledairy (1560s).

[Ann]

---

Wow, Art. You've made 16061 posts. That's a "palindrome number". And impressive, too.

palindrome (n.) "line that reads the same backward and forward," 1620s, from Greek palindromos "a recurrence," literally "a running back." Second element is dromos "a running" (see dromedary); first is palin "again, back."
...........................................
dromedary (n.) "thoroughbred Arabian camel," late 13c., from Old French dromedaire and directly from Late Latin dromedarius "kind of camel," from Latin dromas (genitive dromados), from Greek dromas kamelos "running camel," from dromos "a race course," from dramein "to run." An early variant in English was drumbledairy (1560s).

Drumbledairy should have been a headmaster at Hogwarts. Or some weird milk factory.

Ann