Stellar Evolution Basics
This is the main, long‑lasting stage of a star’s life when it fuses hydrogen into helium in its core.
What is the main sequence?
New stars are born inside these cold, dense regions of gas and dust, often found within larger molecular clouds.
What are dense cores (or star‑forming regions) in molecular clouds
This method detects planets when a star’s brightness drops slightly and periodically as a planet crosses in front of it
What is the transit method?
Kepler’s Third Law states that for planets around the same star, this quantity increases as the cube of the semi‑major axis.
What is the orbital period?
Between a blue star and a red star, this one has the higher surface temperature.
What is the blue star?
On the H–R diagram, these stars lie in a diagonal band from hot and luminous to cool and dim and include the Sun
What are main‑sequence stars?
These regions of ionized hydrogen around hot, young O and B stars often glow red in optical images.
What are H II regions
This technique uses Doppler shifts in a star’s spectrum to detect the tiny back‑and‑forth motion caused by an orbiting planet.
What is the radial‑velocity (or Doppler) method?
A planet orbits a Sun‑like star at about 1 AU. In Earth years, the approximate orbital period is this.
What is about 1 year?
According to Wien’s law, when a star’s surface temperature increases, this happens to the peak wavelength of its emission.
What is it shifts to shorter wavelengths?
Massive stars burn through their fuel faster than low‑mass stars mainly because of this property of their cores.
What is a much higher temperature and pressure (leading to a much higher fusion rate
These small, bright emission patches are created when jets from young stars slam into surrounding gas.
What are Herbig–Haro objects?
Direct imaging works best for planets that are young, hot, and far from their star because they mainly emit strongly in this part of the spectrum.
What is the infrared (IR)?
If a star is moved to twice its original distance, this happens to its parallax angle.
What is it becomes half as large?
A planet at 0.5 AU and one at 1 AU orbit the same Sun‑like star; this one receives more energy per unit area from the star.
What is the planet at 0.5 AU?
Between a red giant and a white dwarf of similar mass, this one is much denser and smaller
What is the white dwarf?
These young, low‑mass pre‑main‑sequence stars are known for variability, strong winds, and surrounding disks.
What are T Tauri stars?
A star’s light curve shows a dip every 10 days with the same depth and shape each time; this repeated pattern reveals this orbital property of the planet.
What is the orbital period (10 days)?
A star has an apparent magnitude of 5 and an absolute magnitude of 0; this tells you about its distance compared to 10 parsecs.
What is it is farther than 10 parsecs?
Planets in the habitable zones of M‑dwarf stars must orbit much closer than Earth orbits the Sun because of this basic property of M‑dwarfs.
What is their much lower luminosity?
Between a G2 V star like the Sun and a B0 I supergiant, this one will leave the main sequence first and in a much shorter time
What is the B0 I star
For a clump in a molecular cloud to collapse into a protostar, its temperature must be low and this quantity must be high enough to overcome internal pressure.
What is density (or mass) so gravity can dominate?
When a planet is seen in transit and also measured with radial velocity, this physical quantity comes mainly from the radial‑velocity data, while radius comes from the transit data.
What is the planet’s mass?
Two planets have the same semi‑major axis, but one orbits a star twice the Sun’s mass. Compared to the other planet, its orbital period is changed in this way.
What is it is shorter (it orbits faster around the more massive star)?
Between a very luminous star and a low‑luminosity star, this one will have a habitable zone that is farther from the star and wider in distance range.
What is the very luminous star?