The First Two Worlds of TESS

Get ready for the avalanche folks! TESS is starting to return science data and already they've discovered two exoplanets. In this episode, I'll let you know more about them.

3153 Views | Published on 22nd Sep, 2018

Hello Space Fans and welcome to another edition of Space Fan News. In this episode, no sooner had I posted my last episode on the TESS First Light image release, that I learned that a paper had come out announcing the first exoplanet discovered by TESS. Boy, that didn’t take long! Then as I was getting ready for Thursday’s Future in Space Hangout and I read about another one. What are the first planets to be discovered by TESS like, and why should we be a little cautious? Stick around to find out.

If you look at the mission status page of the Transiting Exoplanet Survey Satellite, it says that right now TESS has completed observing sector 2 of it’s survey. It is currently in Orbit 12 and downloading it’s latest data stream. TESS looks at each sector for 27 days, which is the time it takes to complete two of its orbits, and it downloads the data it takes after every orbit.

So here we are in Orbit 12, and starting sector three today, Sept 21, and already we have the announcement of two exoplanet discoveries from the mission. What are we to make of this? I say let’s be careful.

TESS launched in April and began its science operations back in July. As I said in the last episode, the satellite is currently searching for planets in the southern sky and these latest results come from the first slice of that survey, called sector 1. There, the spacecraft observed 15,900 stars every two minutes during this initial run, using the transit method of seeing tiny dips in brightness as the exoplanet passes between us and the host star.

So while nothing has been announced by NASA or MIT, who are operating the spacecraft, a paper came out in the preprint archive astro-ph about the first planet candidate. Now before I tell you about these exoplanets, here’s why I urge caution: you need to understand that both of these announcements are based on TESS Alert Data. This data is not available to the general public and is in beta testing to test the alert system out. Since the mission just started and these papers are being sent to AAS Letters and not peer-reviewed, we need to keep this information in context. It’s way to early to say much about this data until the observations are confirmed and the first data release comes out, which won’t be until this coming January.

So with that in mind, the first announcement is about the star Pi Mensae, also known as HD 39091, is an unusually bright yellow subgiant (dwarf) star. This star is visible to the naked eye and is located nearly 60 light-years from Earth. Based on data gathered from July 25 to August 22, the TESS team has concluded that Pi Mensae c, remember we denote planets around stars with small letters starting with b, is a super-Earth. It’s about 2.14 times Earth’s radius and 4.82 times Earth’s mass. The bad news is, Pi Mensae c is way too close to its host star to support life. A single year on this planet lasts just 6.27 days.

The second star is the M class dwarf LHS 3844 and is located 49 light years away. The planet, LHS 3844 b, is measured at 1.32 times the size of the Earth and orbits the planet once every 11 hours.

Both planets fall under the classification of an ultra-short period exoplanet.

If it seems strange to you that these planets have amazingly short years: 6 days and 11 days, that should come as no surprise given that TESS has only been looking at Sector one for 2 orbits (27 days). This is the amount of time TESS is going to be looking at all of the sectors and these quick data alerts are going to be most sensitive to the planets whipping around the star in short periods versus the longer period planets.

So if these planets are confirmed to actually be there and not just some artifact of the beta testing of the alert system, then these planets are both probably uninhabitable. Sorry. They are probably tidally locked around their stars but in the case of LHS 3844 b, there could be liquid water there if it turns out to have any. And I’m gonna be honest here, that little bit in the paper annoys me no end. How can they possibly know that from the meager TESS data they have? But regardless, if confirmed, LHS 3844 b will be one of the closest planets to the Earth, by comparison, TRAPPIST-1 is 39 light years away, so it’s in the neighborhood, making it pretty easy to study.

I’ll have more to say about this on my podcast in a future episode, but I must say I’m concerned about this need to rush to publish. TESS is exciting and the results from this survey will no doubt change and enhance our view of our place in the universe, but NASA’s been accused of ‘excessive optimism’ with JWST and there’s no reason to get that way with TESS data. I just hope astronomers can chill and get this right. This alert system is still being worked out so I’m a little surprised by this. TESS was designed to find candidate planets for follow up by other telescopes and missions, like JWST. I hope these planets turn out to be there, but I think this story says a lot about the current state of science than anything else.

So here we go… The TESS mission is hoping to find hundreds of thousands of planets during it’s two year mission so I doubt there’s any way I’ll be able to keep up with all the discoveries that are bound to come from TESS, but I’ll do my best to keep you posted.

Well that’s it for this episode Space Fans. Patreon Patrons like these bring SFN to you, you wouldn’t get this without their support, so thank you guys. Don’t forget to register you email with deep astronomy dot space to get proper notifications about all of our content postings and our newsletter.

Thank you all for watching and as always, Keep Looking Up!

Links for more reading:
https://tess.mit.edu/observations/
https://arxiv.org/abs/1809.05967
https://arxiv.org/abs/1809.07242

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Comments & Discussion

If this in any indication, we are not going to be able to keep up with the exoplanet numbers!
DAVID MCFADDEN - 22nd Sep, 2018