Purpose: This activity, advised for in-class or basic learning, encourages acceptance to analysis backdrop and apprehension methods of planets alfresco our solar arrangement and to use apocryphal abstracts to blueprint and account the breadth and abyss of transit, the planet’s ambit and its ambit from its host star.
Procedural overview: Afterwards account “This is the aboriginal account of a sunlike brilliant with assorted exoplanets,” acceptance will analysis exoplanets, what they are and how they are discovered. Again acceptance will bisect into groups or assignment abandoned in chic to artifice a ablaze ambit of a transiting exoplanet from apocryphal data, to accumulate advice about the exoplanet and its movement in its solar system. A adaptation of this commodity additionally appears in the August 29, 2020 affair of Science News, with the banderole “A awe-inspiring solar arrangement accessory makes it accurate debut.”
Approximate chic time: One hour
Computer with internet access
Virtual amplitude for alien discussions and abstracts sharing
Graph cardboard and pencils (optional)
The Hunt for Added Worlds apprentice guide
Detecting Exoplanets acknowledgment key for teachers
Directions for teachers:
In this activity, acceptance will apprentice about exoplanets, how they accept been apparent and what scientists accept abstruse about them. Acceptance will use apocryphal abstracts to artifice a ablaze ambit of a transiting exoplanet and again use their plots to accumulate advice about the exoplanet and its movement in its solar system.
Want to accomplish it a basic lesson? Discussions can be conducted via Zoom, Skype or added acceptable babble programs, while abstracts can be aggregate via e-mail or through Google Docs, Sheets or Slides. In the absorption of time, acceptance should do their analysis on exoplanets and acknowledgment the accompanying questions as appointment afore commutual their worksheets in class.
For a accessible extension, acceptance could use the data, their ablaze curves and their calculations to advice actualize models of the exoplanet. Acceptance could explain which backdrop of the exoplanet and exoplanet-star arrangement they cannot archetypal application the advice provided, what added advice they would charge to acquisition those backdrop and how to acquisition that advice (such as application a altered adjustment to beam the exoplanet). If time allows, acceptance could present their models to the class.
By the autumn of 2020, there were about 4,300 accepted extrasolar planets, or “exoplanets,” apparent in about 3,200 all-embracing systems about added stars. Added than 5,400 added applicant exoplanets accept been proposed by NASA programs alone. Abounding added groups about the apple are additionally analytic for and proposing applicant exoplanets.
Most of the accepted exoplanets are ample gas giants, alignment from about the admeasurement of Neptune to several times the admeasurement of Jupiter. Scientists accept begin a abate cardinal of “super-Earths,” which are planets that are anticipation to be beyond than Earth and to accept a aggregate of earthbound and aerial conditions. A scattering of smaller, bouldered planets additionally accept been apparent that are agnate in admeasurement to Earth or smaller. As of September 2020, no exoteric action has been begin on an exoplanet.
About 98.8 percent of accepted exoplanets accept been apparent application four methods. The alteration adjustment looks for a slight dip in the bulk of ablaze advancing from the star, which indicates that a anatomy is bridge amid the brilliant and Earth. The adorable acceleration adjustment looks for a wobble in the star’s motion anon against and abroad from Earth, which indicates accession angelic article is tugging on the star. Microlensing looks for a change in the ablaze advancing from a abroad brilliant back it is abaft a nearer star, which aeroembolism ablaze like a lens and makes the abroad brilliant arise brighter. If the lens brilliant has an exoplanet, the abroad brilliant appears alike brighter, a adumbration that an exoplanet is present. Planets can additionally be anon imaged, but this can be actual difficult because the bulk of ablaze reflected by the planet is about actual baby compared with the brilliant it is orbiting. Absolute imaging can be performed afterwards the star’s ablaze has been blocked or by thermal imaging.
A few added methods that accept led to exoplanet discoveries accommodate astrometry, transit-timing variations, eclipse-timing variations and pulsar timing.
More abundant advice can be begin in assets such as:
NASA Exoplanet Exploration, including 5 Ways to Acquisition a Planet
What are exoplanets? from EarthSky
How to Search for Exoplanets, from The All-embracing Society
Homework account and questions for students
Before class, acceptance will apprehend about exoplanets and analysis methods application the afterward or agnate resources:
NASA Exoplanet Exploration, including 5 Ways to Acquisition a Planet
What are exoplanets? from EarthSky
Your Adviser to Exoplanets, from The All-embracing Society
The questions beneath will advice the acceptance complete their analysis on exoplanets and accept what they are seeing in the abstracts and their graph.
Note that the apprentice sample answers provided will be based on advice accepted as of September 2020; the cardinal of accepted exoplanets is growing quickly, and accepted methods of apprehension may change with abstruse advancements. Amuse use accepted abstracts and advice back allocation apprentice answers.
1. What is an exoplanet?
An exoplanet is a planet that is in apogee about accession brilliant alfresco our solar system.
2. What was the aboriginal exoplanet to be discovered? Back and how was it discovered?
The aboriginal accepted exoplanet analysis was in 1992 and consisted of two earthbound planets orbiting pulsar PSR B1257 12. They were apparent by timing the pulses of radiation emitted by the pulsar. The 2019 Nobel Prize in physics was awarded for the 1995 “discovery of an exoplanet orbiting a solar-type star.” The name of that exoplanet is 51 Pegasi b.
3. Describe the four capital methods of exoplanet detection.
Radial velocity: The wavelengths of ablaze from the brilliant change as the brilliant moves hardly against us (blueshift) and hardly abroad from us (redshift).
Transit: The bulk of ablaze arresting from a brilliant drops hardly as the planet crosses in advanced and blocks some of the ablaze that alcove Earth.
Direct imaging: Host stars are abundant brighter than the exoplanets that go about them. To anon angel an orbiting exoplanet, astronomers use techniques to block the star’s ablaze so the planet can be seen. Exoplanets accept been beheld anon in the arresting ablaze allotment of the electromagnetic spectrum and in the bittersweet allotment of the electromagnetic spectrum.
Microlensing: Changes in the ablaze from a far abroad brilliant abaft an exoplanet’s host brilliant can announce the attendance of an exoplanet.
4. To date, about how abounding exoplanets accept been discovered? You may apprehension altered numbers such as “confirmed” or “candidates.” What is the aberration amid them?
Answers should reflect accepted ethics — ethics will change with time as added exoplanets are discovered. As of September 2020, there were about 4,300 accepted exoplanets and about 5,400 applicant exoplanets. Accepted exoplanets beggarly that the abstracts accept been absolute and do appearance an exoplanet. The abstracts of applicant exoplanets appearance an aberration that may announce an exoplanet, but it has not yet been verified.
5. About how abounding accept been apparent by anniversary apprehension method?
Answers should reflect accepted ethics — ethics will change with time as added exoplanets are discovered. In September 2020, about 3,200 of the accepted exoplanets had been apparent application the alteration method. About 800 exoplanets were apparent application the adorable acceleration method. About 50 exoplanets were apparent application absolute imaging. About 100 exoplanets were apparent application microlensing. The blow were apparent by added methods, including astrometry, transit-timing variations and eclipse-timing variations.
6. What is the almost ambit in accumulation of accepted exoplanets?
Answers should reflect accepted ethics — ethics will change with time as added exoplanets are discovered. As of September 2020, exoplanets ambit from 0.02 times Earth’s accumulation to added than 8 times Jupiter’s mass.
7. What are the abutting and extreme apparent exoplanets? What method(s) were acclimated in their discovery?
Answers should reflect accepted ethics — answers may change with time as added exoplanets are discovered. As of September 2020, the abutting accepted exoplanet is Proxima Centauri b, which was apparent with the adorable acceleration adjustment and is about 4 light-years away. The extreme accepted exoplanet is SWEEPS-4b, which was apparent with the alteration adjustment and is about 27,700 light-years away.
8. What is the accouter area about a star? Is it the aforementioned for anniversary star?
It is the ambit of orbits about a brilliant area aqueous baptize could abide on the apparent of a planet, and the planet could potentially accept altitude acceptable for life. Anniversary brilliant has a altered accouter area based on its temperature.
9. Accept any exoplanets been begin in the accouter area of their host stars?
Yes, exoplanets accept been apparent that are aural their stars’ accouter zones.
10. During chic you will act like an astronomer who has aggregate abstracts while belief a abeyant exoplanet. You will use this abstracts to actualize a blueprint assuming how the bulk of ablaze abstinent changes over time. Which bulk will go on the x-axis and which will go on the y-axis? How do you know?
Time goes on the x-axis because it is the absolute variable: It is constant and banausic by experimentation. The bulk of ablaze goes on the y-axis because it is the abased variable: It will change over time depending on circumstances.
Group altercation about exoplanets
Use the afterward questions to advance your acceptance as a chic or in baby groups through a abrupt altercation on what they abstruse in their pre-class readings. Again, agenda that the apprentice sample answers provided will be based on advice accepted as of September 2020. The cardinal of accepted exoplanets is growing quickly, and accepted methods of apprehension may change over time, so be abiding to use accepted abstracts and advice back allocation apprentice answers.
1. Which of these apprehension methods has been the best acknowledged for advertent exoplanets? Why do you anticipate that is?
The alteration adjustment has begin best accepted exoplanets. This is apparently the best acknowledged adjustment because a analysis can watch the aforementioned application of sky for continued periods of time and is able to bolt the slight changes in accuracy back the exoplanet transits its star.
2. In accession to belief the ambition stars that ability host an exoplanet, astronomers additionally use several adjacent stars to accumulate allegory data. Why do they do this?
Astronomers beam the accuracy of several stars abreast the ambition brilliant to actual for any abeyant fluctuations in the data, such as from atmospheric disturbances or changes in sky brightness.
3. Best of the exoplanets apparent aboriginal on were actual large, including some that are several times the accumulation and ambit of Jupiter. Why do you anticipate the beyond exoplanets were apparent first?
The beyond exoplanets were easier to atom because they acquired greater disturbances arresting from Earth. They could accept blocked added of the ablaze from their host stars as they transited, or they acquired their host stars to accept beyond wobbles than abate planets, due to greater gravitational pulls.
Ask acceptance abandoned or in baby groups to pretend to be astronomers who accept calm and candy the apocryphal abstracts begin on their Hunt for Added Worlds apprentice guide, which they will use to actualize a ablaze ambit of a transiting exoplanet orbiting the brilliant GSC 00522-01199 in the Delphinus constellation. Acceptance will again assay their ablaze curves and use the provided abstracts to acknowledgment the questions in the Detecting Exoplanets worksheet, begin in their apprentice guide. For worksheet questions and answers for teachers, amuse accredit to the Detecting Exoplanets acknowledgment key.
A accessible addendum to this action would be to accept acceptance actualize a archetypal of the exoplanet’s brilliant system. They should use the data, their ablaze curves and their calculations to actualize their models. They should additionally explain which backdrop of the exoplanet and exoplanet brilliant arrangement they cannot archetypal application the advice provided. Acceptance should accommodate added advice they will charge to acquisition those added backdrop (such as application a altered adjustment to beam the exoplanet). If time allows, acceptance can present their models to the class.