ASTRO 7N - Unit 3, Part 2: Nearby Stars Lesson

The next star in the Alpha Centauri triple-star system, Alpha Centauri AB, is 2 AU away and has a parallax angle of 16.7 arc seconds from our current position at Proxima Centauri. The distance from our current location to Alpha Centauri AB is about:

0.06 parsecs

Distance in parsecs equals...

1 over the parallax angle in arc seconds

The parallax angle for Alpha Centauri is 0.74 arc seconds. The distance to Alpha Centauri is:

1.35 parsecs (1 parsec ~3.26 light years) (takes over 4 years to get there)

The parallax angle to the next star, Barnard's star, is 0.56 arc seconds. What is the distance to Barnard's star?

1.79 parsecs

Sirius is a binary star. What is spectral type of Sirius A?

A0

What spectral type is Rigel?

A0

What spectral type is Sirius A?

A0

What spectral type is Vega?

A0

What spectral type is Achernar?

B5

We have made it to a bunch of stars and they all seem pretty similar to one another. All of them:

Except one (Sirius A & B) are redder and less luminous than the sun

Canopus is the second-brightest star in the nighttime sky. On Earth it can be seen from locations in or near the southern hemisphere. What spectral type is Canopus?

F0

What spectral type is Procyon?

F5

Alpha Centauri A (the brightest of the three stars in Alpha Centauri) has a luminosity of 1.6 Suns and a spectral type closest to:

G0

What spectral type is α (Alpha) Centauri A?

G0

Which one of the listed star spectrums looks the most like the spectrum of our sun?

G0 (star 6,000 K)

What spectral type is Capella?

G5

Alpha Centauri B is a dimmer-looking orange star near Alpha Centauri A. It is only 24 AU away from Alpha Centauri A. This star is closer to the last star than Neptune is to the sun. Alpha Centauri B has a luminosity of 0.5 Suns and a spectral type closest to:

K0

What spectral type is Arcturus?

K0

What spectral type is ε (Epsilon) Eridani?

K0

What spectral type is Betelgeuse?

M0

What spectral type is Lacaille 9352?

M0

BL Ceti is a binary star. What spectral type is BL Ceti A?

M5

Barnard's Star is a little red star. What spectral class is it?

M5

The little red one, Proxima Centauri, is the spectral type:

M5

What is the spectral type of Lalande 21185?

M5

What is the spectral type of Wolf 359?

M5

What spectral type is BL Ceti B?

M5

What spectral type is Ross 154?

M5

What spectral type is Ross 248?

M5

The absorption lines of a spectrum are:

Produced when photons of specific wavelengths are absorbed in a star's outer layers by the electrons of specific chemical elements

Brightest stars as seen from Earth or Mars:

Sirius A and Sol

For a distance closest to 1 parsec, you should use warp factor 1, for 2 parsecs use warp factor 2, and for 3 parsecs use warp factor 2. Since Alpha Centauri is at 1.35 parsecs, we should use:

Warp 1

On the map, it seems that Canopus is...

a lot farther away than any of the nearest stars that we've looked at

The difference in luminosity is really large. How many times greater is the luminosity of Sirius A than Sirius B, the white dwarf?

almost 1000 times

The stars that can be seen most easily from Earth or Mar would have to be bright ones, and if they were hotter then they would be...

bluer and on the left part of our HR diagram

HR diagram

graph with the luminosity of a star on the vertical/y-axis and the temperature or spectral class on the horizontal/x-axis

Procyon...

isn't quite as luminous as any of the others, but it can still appear bright because it is relatively closer to the sun.

Proxima Centauri is in the lower right of the HR diagram, which seems to correspond to __________ temperatures and __________ luminosities.

low; low

Canopus is...

more luminous than all the other stars so far. That must be why it looks so bright even at this large distance.

Alpha Centauri A is __________ the sun in the HR diagram, and the dot is a bit larger than the dot for the sun since the star is __________.

right next to; bigger

The spectrum gives the temperature. The scan also gives the luminosity. Luminosity is:

the absolute amount of energy a star produces in a second, like the wattage (solar luminosity) of a lightbulb

Sirius A has a white dwarf, Sirius B, in the same binary system. But Sirius B isn't included in this list of brightest stars, because Sirius A and B are the same distance from our Sun, so Sirius B,

the white dwarf, isn't very luminous and so it appears faint compared to the much more luminous Sirius A

The white dot to the left of Sirius A is Sirius B and is a white dwarf. Sirius B is __________ the sun in the HR diagram and is __________ compared to the sun.

to the (far) lower left; smaller (and brighter)

Lacaille 9352 is __________ the sun in the HR diagram and is __________ compared to the sun.

to the (far) lower right; slightly smaller (and dimmer) (to the slight upper right of Lalande 21185)

Ross 248 is __________ the sun in the HR diagram and is __________ compared to the sun.

to the (far) lower right; smaller (and dimmer) (right on top of Barnard's Star)

BL Ceti A is __________ the sun in the HR diagram and is __________ compared to the sun.

to the (far) lower right; smaller (and dimmer) (right on top of Proxima Centauri)

Ross 154 is __________ the sun in the HR diagram and is __________ compared to the sun.

to the (far) lower right; smaller (and dimmer) (to the slight lower left of Barnard's star)

BL Ceti B is __________ the sun in the HR diagram and is __________ compared to the sun.

to the (far) lower right; smaller (and dimmer) (to the slight right of Wolf 359)

Alpha Centauri B is __________ the sun in the HR diagram and is __________ compared to the sun.

to the (far) lower right; the same size

ε Eridani is __________ the sun in the HR diagram and is __________ compared to the sun.

to the (slight) lower right; slightly smaller (and dimmer) ("right" next to Alpha Centauri B)

Wolf 359 is __________ the sun in the HR diagram and is __________ compared to the sun.

to the lower right; smaller (and redder) (slightly to the right of Proxima Centauri)

Lalande 21185 is __________ the sun in the HR diagram and is __________ compared to the sun.

to the lower right; smaller (and redder) (to the upper left of Barnard's Star)

Barnard's Star is __________ the sun in the HR diagram and is __________ compared to the sun.

to the lower right; smaller (and redder) (to the upper left of Proxima Centauri)

Achernar is __________ the sun in the HR diagram and is __________ compared to the sun.

to the upper (far) left; slightly bigger (and brighter) (upper left of Sirius A and Vega)

Sirius A is __________ the sun in the HR diagram and is __________ compared to the sun.

to the upper left; larger (and brighter)

Canopus is __________ the sun in the HR diagram and is __________ compared to the sun.

to the upper left; much larger (and brighter) (to the upper right of Sirius A)

Rigel is __________ the sun in the HR diagram and is __________ compared to the sun.

to the upper left; much larger (and brighter) (upper left of Sirius A and Vega)

Procyon is __________ the sun in the HR diagram and is __________ compared to the sun.

to the upper left; slightly bigger (and brighter) (also upper left of α Centauri B)

Betelgeuse is __________ the sun in the HR diagram and is __________ compared to the sun.

to the upper right; much bigger (redder and brighter) (upper right of Capella and Vega)

Capella is __________ the sun in the HR diagram and is __________ compared to the sun.

to the upper right; much larger (and brighter) (right to the lower left of Vega)

Arcturus is __________ the sun in the HR diagram and is __________ compared to the sun.

to the upper right; much larger (and brighter) (to the lower right of Canopus)

Vega is __________ the sun in the HR diagram and is __________ compared to the sun.

to the upper right; much larger (redder and brighter) (right above Sirius A)

HR diagram. I admit I'm interested in seeing where these nearby stars lie on it. So far there is one like the sun and...

two cooler ones